Unlike broad-edged calligraphy, the x-height is not measured in terms of nib widths. Typical x-heights are 4, 5 or 6mm. The ‘normal’ ratio of ascender – x-height – descender is 3:2:3. Therefore if you have an x-height of 4mm, you would have 6mm for ascenders and descenders. However, these are only guidelines.
Copperplate writing has a steep slope, usually 55° from the horizontal. It can be hard to write at such a steep angle (especially if you are right-handed). This is why a right-handed calligrapher will typically use an oblique pen holder to help ‘point’ the nib in the right direction. A left-handed calligrapher, holding a straight pen holder will automatically have their nib at an angle close to the required 55°. If you are right-handed, rotating the paper in an anti-clockwise direction can help you achieve the correct pen angle. Left handed calligraphers usually they prefer to keep the paper straight. These are only guidelines – experiment to find the combination of pen holder, nib type and paper angle that is most comfortable for you.
It is useful to construct the 55° line on you guideline sheet. Once you have constructed the first line it can be easily duplicated across the paper by using the width of the ruler to produce a line parallel to the original line. Now slide the ruler over to this second guideline and draw in the third line. This process can be repeated across the whole page.
It is worth spending time accurately producing a guide sheet as it can be photocopied at different enlargement settings to produce several guide sheets at various x-heights. If you do this you will need to have heavy but fine lines. You could use a fine black pen to do this.
(It is advisable to check the printer options to make sure there are no ‘fit to print’ or other settings that may alter the size of the printout).